Percutaneous transluminal angioplasty (PTCA) has been an important therapy in ischemic heart disease. However, its limitation is restenosis which occurs in 25-55% of patients after PTCA within 6 months. The main cause of restenosis is proliferation of smooth muscle cells. If we can prevent the proliferation of smooth muscle cells, PTCA will be a more effective therapy. We have been trying to inhibit smooth muscle cell proliferation. We are employing antisense strategy to inhibit the proliferation of smooth muscle cells. Antisense oligodeoxynucleotides are complementary to normal mRNA. They hybridize to the mRNA, and thereby inhibit the translation of mRNA so that the protein encoded by the specific mRNA targeted is not expressed. We hypothesized that if we could inhibit expression of factors that are necessary for cell proliferation, we could actually inhibit proliferation. This year we found that anti-sense oligodeoxynucleotide complementary to c-myc mRNA did inhibit the proliferation of smooth muscle cells in vitro.